In recent years, online transactions through the Internet or the like have been increased. Such online transactions are required to ensure sufficient security. Conventionally, in addition to identity verification using biometrics, Public Key Infrastructure (PKI) authentication and the like have been implemented in order to ensure security. The present applicants have proposed, in Japanese Patent Application Laid-Open No. 2004-157790 for example, a security judgment method by combining biometric authentication, PKI authentication and authentication based on environmental information of a machine (device).